1. Field of Invention
The invention relates to bicycles and other human powered machines. More specifically to a bicycle pedal having a pedal body, rotatably supported by bearings, on a pedal axle which affixes to a crankarm of a bicycle.
2. Description of Prior Art
The axles and bearings of bicycle pedals are subjected to high static and dynamic loads. Competitive and serious cycling enthusiasts, in particular, commonly place very high demands on these components of a bicycle pedal. This has led to the premature and sometimes unsafe failures of these components in many bicycle pedals.
The axle and bearing arrangement used in conventional pedal designs, incorporate an inner and an outer row of ball bearings with an adequately proportioned, relatively long pedal axle. The inner row of ball bearings is typically located approximately beneath the inside edge of where the cyclist's foot contacts with the pedal, and correspondingly, the outer row of balls is located approximately beneath the outside edge of the cyclist's foot. Designs of this type have the advantage of rather evenly distributing the loads, which are generated by the cyclist, between these two sets of bearings. This allows the sets of bearings to wear nearly evenly, thus preventing one of the set of bearings from wearing out prematurely. The overall life span and time intervals between servicing the pedals are relatively long with this type of design.
A disadvantage of this type of design, however, is that the diameter of the pedal body around the rows of bearings is relatively large. And, because these rows of bearings are placed directly beneath the cyclist's foot, this results in the cyclist's foot being displaced a rather sizable distance away from the pedal axle. This relatively large distance reduces the stability of the cyclist's foot on the pedal, as well as, reduces the efficient energy transfer from the cyclist through the pedals. Therefore, these pedals have lessened comfort and efficiency when compared to more modem pedal designs that incorporate lower profile types of bearing arrangements, which bring the cyclist's foot closer to the pedal axle.
Another disadvantage of this conventional type of pedal design is that, due to the relatively long length of the axle, the outer edge of the pedal body is a considerable distance away from the bicycle's crankarm. This increases the likelihood of the pedal body striking the ground while pedaling through a comer, which is potentially dangerous, and a serious disadvantage to competitive cyclists who need to be able to pedal through turns to keep up their momentum.
A further disadvantage associated with these pedals is their relatively large size and heavy weight which makes them less efficient and aerodynamic, overall.
U.S. Pat. No. 4,882,946 describes a different type of axle and bearing arrangement intended to improve upon some of the disadvantages of the more conventional type which was just described. In a similar fashion as the conventional arrangement, this design uses a relatively large diameter, inner row of ball bearings, for carrying the inner portion of the loads generated by the cyclist. However, instead of placing this inner row of bearings directly beneath the inside of the cyclist's shoe, as in the conventional design, they are moved to the inside, out from under the cyclist's shoe, as close as possible to the crank arm of the bicycle.
A much smaller in diameter row of needle roller bearings, is used in conjunction with the inner row of ball bearings to support the radial loads applied by the cyclist. Despite their relatively small diameter, the line type of contact which needle rollers make, with their mating raceway surfaces, gives them the capability of carrying the entire radial loads generated by the cyclist. This enables them to be placed more directly beneath the center of the cyclist's foot. Therefore, the larger diameter inner row of ball bearings carry the entire thrust loads, while also positioning the pedal body on the axle, and the smaller diameter, outer row of needle bearings support nearly the entire radial load. This allows the treading surface of the pedal body to be located closer to the axle than the larger diameter portion of the pedal body which houses the inner row of ball bearings. This advantageously brings the cyclist's foot closer to the pedal spindle, for improved stability and efficiency. Also, because the outer row of needle bearings are placed closer to the center of the pedal body, beneath the cyclist's foot, the axle is made shorter than in a conventional designs. This enables the outer, bottom portion of the pedal body to be cut away, thus increasing the pedals clearance while leaning the bicycle which improves safety and cornering ability.
Though this design does offer advantages over the more conventional pedal design, there are disadvantages of the design. The larger diameter portion of the pedal body housing, which contains the inner row of ball bearings, is sufficiently wide to cause axial displacement of the cyclist's shoes and feet, which can result in poor biomechanical alignment of the leg joints of some cyclists. This decreases efficiency and can lead to stress induced injuries with cyclists whom need their feet placed more closely to the inside of the pedal due to their particular anatomy.
Another disadvantage of this design is the relatively heavy weight of the pedals. This is due to the extended length and increased diameter of the pedal body which is necessary to accommodate the size and location of the inner bearing.
U.S. Pat. No. 5,379,665 describes various axles and bearing arrangements using two, relatively small diameter, rows of ball bearings, in conjunction with a single row of needle bearings. The embodiment shown in FIG. 1 incorporates a relatively short axle which advantageously enables the cutting away of the outer, bottom side of the pedal body, for improved cornering ability.
A serious disadvantage of this design, however, is the relatively low load rating and close spacing of the two, inner and outer, rows of ball bearings. If the center of the load applied by the cyclist is not closely positioned over the central row of needle roller bearings, but rather, as is common while riding, is centered over the far inside or outside areas of the pedal body, overloading of the ball bearings can occur. This causes the pedals to require frequent rebuilding which is expensive and inconvenient for the cyclist.
Further, the close spacing of the rows of ball bearings gives poor lateral stability to the pedal body, which can result in the pedal body rubbing against the axle when the center of the load applied by the cyclist is over the far inside, or outside, of the pedal body. This rubbing causes undesirable friction, decreasing efficiency.
Yet another disadvantage of this design is the placement of the row of relatively large diameter ball bearings, on the larger diameter section of the axle, located to the inside of the row of needle roller bearings. This increases the overall height of the pedal body, negating the low profile benefit of the needle roller bearings, disadvantageously resulting in the cyclist's foot being placed higher above the pedal axle than is possible in other designs.
An examination of the alternative axle and bearing arrangement as shown in FIG. 3 of the same patent, reveals that this design shares the same disadvantages of the previously discussed design. Once again, the use of relatively low load rated ball bearings on the outside of the pedal axle, where the loads applied by the cyclist are often concentrated, results in these bearings being easily overloaded. Also, the close spacing of the inner and outer bearings causes poor lateral stability of the pedal body. Additionally, the relatively large cross section of the pedal body results in the cyclist's foot being placed an undesirable distance above the pedal axle.
FIG. 4 of the same patent shows yet another embodiment in which needle roller bearings are placed to the outside of the axle. A major disadvantage of this design is the significantly reduced axle strength caused by the decreased axle diameter which is required to install the outer raceway used with the ball bearings. Additionally, the undesirable height of the pedal body is unchanged from the other embodiments.
A further disadvantage of bicycle pedals, in general, is the lack of a simple means for maintaining and lubricating the axle bearings. Because pedals are sometimes subjected to harsh operating environments, which lead to rapid deterioration of the bearings if they are not properly maintained, it is desirable to have a quick and simple method of lubricating and cleansing the bearings of contaminants. In many systems, it is necessary to disassemble the pedal for cleaning and relubrication. This is time consuming and can be expensive, often causing it to be neglected, which results in the premature failure of the components of the bearing system.
It would be advantageous to have a means for simply lubricating the bearings of a pedal quickly and without requiring special tools or disassembly. Additionally, ideally the lubrication process would also serve to cleanse the axle seals and bearings of any contaminants that may have worked into them. In this way disassembly for cleaning and lubrication would never be required.